Bovine endometrial cells do not mount an inflammatory response to Leptospira

Leptospira spp. is recognized by TLR2 and induces IFN-β and IFN-λ expression in smegma from naturally infected bulls

Leptospirosis, a zoonosis with a wide worldwide distribution, causes significant reproductive losses in cattle. The genital presentation of the disease has been reported, and its understanding is crucial for the implementation of adequate sanitary measures. Although Leptospira spp. modulate innate immunity, the response in the genital mucosa of bulls is unknown. The objective of this work was to evaluate the expression of innate immune receptors and cytokines in smegma from bulls with genital infection by Leptospira spp. To do so, routine preputial scraping samples were selected from breeding bulls from four establishments in the Azul District, Buenos Aires, Argentina with no reproductive problems, which were previously evaluated for the presence of Leptospira spp. DNA by qPCR detection of the secY gene. The relative gene expression of TLR2, TLR4, IFN-β and IFN-λ in the smegma samples of animals infected with Leptospira spp. was determined by RT-qPCR, with subsequent analysis of the results using REST software. The expression of TLR2 was significantly increased in animals infected with Leptospira spp. compared to uninfected control animals (4-fold), while TLR4 did not show differences. Likewise, both IFN-β and IFN-λ were significantly increased in smegma of infected animals (3.5 and 3.1-fold, respectively). Therefore, this work shows that genital infection of Leptospira spp. in bulls generates and modulates a local innate immune response, with an association between the presence of Leptospira spp. DNA and the expression levels of TLR2, IFN-β and IFN-λ.

Cellular inflammatory response in the bovine uterus by Leptospira infection may be related to embryo death and subfertility

Bovine leptospirosis is a chronic disease that causes various reproductive disorders and consequent economic losses worldwide, particularly embryo death. Although Leptospira spp. has already been detected in the genital tract of cows, little is known about the uterine cellular immune response or the intrinsic factors that could contribute to that reproductive failure. In this context, the aim of this study was to assess the uterine cellular inflammatory response after the quantification of cytokine IL-6 in bovine uteri naturally infected with leptospires compared to uninfected. Our results demonstrated that uterine tissues infected with leptospires have higher levels of IL-6 compared to uninfected tissues (p < 0.001). It suggests that the presence of leptospires in the bovine uterus can induce a cellular inflammatory response, which may be related to embryo death and consequent subfertility.

MiR-495-3p attenuates cell pyroptosis and endometritis through inhibiting the activation of NLRP3 inflammasome in bovine

miR-495 is aberrantly expressed and affects the progression of inflammation in various diseases. However, the mechanisms of miR-495 in bovine endometritis remain largely unknown. This study investigated the mechanism of miR-495 in lipopolysaccharide (LPS)-induced bovine endometritis and pyroptosis and found that miR-495 inhibits NLRP3 inflammasome activation and inflammatory immune responses in endometritis tissue and cell models. Bovine endometrial epithelial cells (BENDs) were treated with 10 μg/mL LPS to establish a cell inflammatory model. LPS stimulation activated the NLRP3 inflammasome and elevated the expression of proinflammatory factors in BEND cells. In addition, pyroptosis and methylation-dependent inhibition of miR-495 was discovered in LPS-exposed BENDs. Furthermore, overexpression of miR-495 inhibited activation of the NLRP3 inflammasome in vitro and vivo. Collectively, our data demonstrate that miR-495 can attenuate activation of the NLRP3 inflammasome to protect against pyroptosis and bovine endometritis, which provides novel therapeutic targets for bovine endometritis and other inflammatory diseases.

Transient Presence of Live Leptospira interrogans in Murine Testes

Analysis of Leptospira dissemination and colonization of sex organs in rodents is of significant value as it queries the possibility of mammal-to-mammal venereal transmission. The aim of our study was to evaluate the presence and viability of Leptospira interrogans in testes of mice using models of infection that we previously developed. Using sublethal and lethal doses of bioluminescent strains of L. interrogans serovars Manilae and Copenhageni, we visualized the presence of leptospires in testes of C57BL/6 mice as early as 30 min and up to days 3-4 postinfection. This was confirmed by qPCR for the Copenhageni serovar after lethal infection of C3H/HeJ mice. In this model, no histopathological changes were noticed in testis. We further studied persistence of serovar Copenhageni in C3H/HeJ testes after lethal and sublethal infection, with different doses of leptospires. No viable leptospires were recovered from testes of lethally infected mice. However, we found live culturable Leptospira in testes of 19/19 (100%) sublethally infected mice at the acute phase but not at 15 days postinfection, which corresponds to the chronic phase of renal colonization. The data suggest that colonization of testes with live and potentially infectious leptospires is transient and limited to the spirochetemic phase of infection. Further studies are necessary to evaluate if presence of Leptospira in testes of mice leads to excretion in semen and to venereal transmission to female mice. IMPORTANCE Analysis of venereal transmission of Leptospira is important to determine if direct animal to animal transmission occurs, which could impact measures to prevent and treat leptospirosis. The goal of this study was to determine if live Leptospira colonize mouse testes. We found that colonization of mouse testes with live Leptospira was transient and limited to the acute spirochetemic phase of infection and that transient colonization of the testes was insufficient to cause histopathological changes.

Bovine Leptospirosis Due to Persistent Renal Carriage of Leptospira borgpetersenii Serovar Tarassovi

Leptospirosis is a global zoonotic disease that causes significant morbidity and mortality in human and animal populations. Leptospira interrogans is a leading cause of human disease, and L. borgpetersenii is a leading cause of animal disease. Cattle are reservoir hosts of L. borgpetersenii serovar Hardjo, which is transmitted via urine, semen, and uterine discharges resulting in abortion and poor reproductive performance. Bovine bacterin vaccines can only protect against those serovars included in vaccine formulations and typically include serovar Hardjo among others. Genotyping and serotyping represent two different and unique methods for classifying leptospires that do not always correlate well; comprehensive characterization using either method requires recovery of isolates from infected animals. In this study, we report for the first time, isolation of L. borgpetersenii serovar Tarassovi from the urine of a dairy cow in the U.S. The classification of the isolate, designated strain MN900, was confirmed by whole-genome sequencing, serotyping with reference antisera and monoclonal antibodies, Matrix Assisted Laser Desorption/Ionization (MALDI), and immunoblotting with reference antisera. Strain MN900 was excreted in urine samples for 18 weeks even as the cow was seronegative for serovar Tarassovi. Strain MN900 has an unusual morphology since it is not as motile as other leptospires and lacks hooked ends. Serovar Tarassovi is not included in U.S. bacterin vaccines. These results demonstrate the importance of culture and concomitant genotyping and serotyping to accurately classify leptospires, and as required to design efficacious vaccine and diagnostic strategies to not only limit animal disease but reduce zoonotic risk.